This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. This proposal is part of our ongoing structural studies aimed at the characterization of all the domains of the hER, biochemically important mutants of these domains, and evaluation of potential therapeutic targets. We have been working on the structural characterization of the human Estrogen Receptor (hER) ligand binding domain (LBD) complexes with potential therapeutic small molecules since the Spring of 2005. These compounds have encompassed those with novel scaffolds, varying potency and selectivity for the different isoforms of hER. We have recently begun to characterize the other domains of hERalpha (besides the LBD). We have obtained crystals of A though D domains of both the wild type and point mutant proteins expressed as fusion products with the maltose binding protein (MBP). These MBP fusion proteins are soluble and have crystallized in several conditions of our intial screens. This is exciting progress because we have no structural knowledge to date, of the three dimensional organization of the various domains of hER. We need beam time to screen these crystals of various length of hER for diffraction quality, so we can optimize the conditions for better crystals. We also hope to collect a few datasets.